Semiconductor light emitting device and method of manufacturing the same

ABSTRACT

Provided are a semiconductor light emitting device and a method of manufacturing the same. The semiconductor light emitting device comprises a first conductive type semiconductor layer, an active layer, a first thin insulating layer, and a second conductive type semiconductor layer. The active layer is formed on the first conductive type semiconductor layer. The first thin insulating layer is formed on the active layer. The second conductive type semiconductor layer is formed on the thin insulating layer.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of co-pending U.S. patentapplication Ser. No. 13/551,382, filed on Jul. 17, 2012, which is acontinuation of U.S. patent application Ser. No. 12/187,970, filed onAug. 7, 2008, now U.S. Pat. No. 8,237,181, which claims priority under35 U.S.C. 119 to Korean Patent Application No. 10-2007-0080102 filed onAug. 9, 2007, which is hereby incorporated by reference in its entirety.

BACKGROUND

The present disclosure relates to a semiconductor light emitting deviceand a method of manufacturing the same.

Groups III-V nitride semiconductors have been variously applied to anoptical device such as blue and green light emitting diodes (LED), ahigh speed switching device, such as a MOSFET (Metal Semiconductor FieldEffect Transistor) and an HEMT (Hetero junction Field EffectTransistors), and a light source of a lighting device or a displaydevice.

The nitride semiconductor is mainly used for the LED (Light EmittingDiode) or an LD (laser diode), and studies have been continuouslyconducted to improve the manufacturing process or a light efficiency ofthe nitride semiconductor.

SUMMARY

Embodiments provide a semiconductor light emitting device comprising athin insulating layer on an active layer and a method of manufacturingthe same.

Embodiments provide a semiconductor light emitting device comprising athin insulating layer using a P-type dopant between an active layer anda second conductive type semiconductor layer and a method ofmanufacturing the same.

Embodiments provide a semiconductor light emitting device, where atleast one thin insulating layer is formed between an active layer and anelectrode layer to diffuse holes and decrease a leakage current, and amethod of manufacturing the same.

An embodiment provides a semiconductor light emitting device comprising:A semiconductor light emitting device, comprising: a first conductivetype semiconductor layer; an active layer formed on the first conductivetype semiconductor layer; a second conductive type semiconductor layerincluding a first semiconductor layer formed on the active layer and asecond semiconductor layer formed on the first semiconductor layer; athird semiconductor layer disposed between the first semiconductor layerand the second semiconductor layer; a first electrode electricallyconnected to the first conductive type semiconductor layer; and a secondelectrode electrically connected to the second conductive typesemiconductor layer, wherein the third semiconductor layer is physicallycontacted with an lower surface of the second semiconductor layer,wherein the third semiconductor layer has a P-type dopant concentrationless than that of the first and second semiconductor layers, wherein thethird semiconductor layer has a hole concentration of about 5×10¹⁸/cm³or less and has a greater resistivity than that of the firstsemiconductor layer.

An embodiment provides a semiconductor light emitting device comprising:semiconductor light emitting device, comprising: a first conductivesemiconductor layer including an n-type dopant; a second conductivesemiconductor layer including an p-type dopant; an active layer betweenthe first conductive semiconductor layer and the second conductivesemiconductor layer; a first semiconductor layer between the activelayer and the second conductive semiconductor layer; a secondsemiconductor layer on the second conductive semiconductor layer,wherein the second conductive semiconductor layer is physicallycontacted with the first and second semiconductor layers, wherein thefirst and second semiconductor layers have a greater resistivity thanthat of the second conductive semiconductor layer, wherein the first andsecond semiconductor layers have a hole concentration less than that ofthe second conductive semiconductor layer.

An embodiment provides a method of manufacturing a semiconductor lightemitting device, the method comprising: forming a first conductive typesemiconductor layer; forming an active layer on the first conductivetype semiconductor layer; forming a first thin insulating layer on theactive layer; and forming a second conductive type semiconductor layeron the first thin insulating layer.

The details of one or more embodiments are set forth in the accompanyingdrawings and the description below. Other features will be apparent fromthe description and drawings, and from the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side sectional view of a semiconductor light emitting deviceaccording to a first embodiment.

FIG. 2 is a side sectional view of a semiconductor light emitting deviceaccording to a second embodiment.

FIG. 3 is a side sectional view of a lateral semiconductor lightemitting device using FIG. 1.

FIG. 4 is a side sectional view of a vertical semiconductor lightemitting device using FIG. 1.

FIG. 5 is a reverse current versus voltage graph for a related art LEDand an LED according to a first embodiment.

FIG. 6 is a forward current versus voltage graph for a related art LEDand an LED according to a first embodiment.

FIG. 7 is a graph showing a reliability test for a related art LED andan LED according to a first embodiment for a predetermined time.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Hereinafter, semiconductor light emitting devices and methods ofmanufacturing the same in accordance with embodiments will be describedwith reference to the accompanying drawings. Reference will now be madein detail to the embodiments of the present disclosure, examples ofwhich are illustrated in the accompanying drawings. In the followingdescription, words “above,” “one,” “below,” and “underneath” are basedon the accompanying drawings. In addition, a thickness of each layer isonly exemplarily illustrated.

FIG. 1 is a side sectional view of a semiconductor light emitting deviceaccording to a first embodiment.

Referring to FIG. 1, a semiconductor light emitting device 100 comprisesa substrate 110, a buffer layer 120, an undoped semiconductor layer 130,a first conductive type semiconductor layer 140, an active layer 150, athin insulating layer 160, and a second conductive type semiconductorlayer 170.

The substrate 110 may be formed of one selected from the groupconsisting of sapphire (Al₂O₃), GaN, Sic, ZnO, Si, GaP, GaAs, and InP.Also, the substrate 110 may comprise a conductive substrate. However, amaterial of the substrate 110 should not be limited thereto.

A nitride semiconductor is grown on the substrate 110 using a growthdevice. The growth device may comprise an E-beam evaporator, a physicalvapor deposition (PVD) apparatus, a chemical vapor deposition (CVD)apparatus, a plasma laser deposition (PLD) apparatus, a dual-typethermal evaporator sputtering apparatus, a metal organic chemical vapordeposition apparatus, but not limited thereto.

The buffer layer 120 is formed on the substrate 110, and the undopedsemiconductor layer 130 is disposed on the buffer layer 120. Here, thebuffer layer 120 decreases a lattice constant difference between thenitride semiconductor and the substrate 110 and may selectively compriseGaN, AlN, AlGaN, InGaN, or the like. The undoped semiconductor layer 130may be formed as an undoped GaN layer and serves as a substrate forgrowth of a nitride semiconductor. At least one or neither of the bufferlayer 120 and the undoped semiconductor layer 130 may be formed on thesubstrate 110, but not limited thereto.

The first conductive type semiconductor layer 140 is formed on theundoped semiconductor layer 130. The first conductive type semiconductorlayer 140 may be formed as an electrode contact layer doped with a firstconductive type dopant. The first conductive type semiconductor layer140 may be formed as an N-type semiconductor layer. The N-typesemiconductor layer may comprise a compound of a group III element and agroup V element, for example, a semiconductor material having acomposition ratio of In_(x)Al_(y)Ga_(1-x-y)N (0≦x≦1, 0≦y≦1, 1≦x+y≦1).That is, the N-type semiconductor layer may comprise at least one ofGaN, InN, AlN, InGaN, AlGaN, InAlGaN, and AlInN. The first conductivetype dopant is an N-type dopant, and the N-type dopant comprises Si, Ge,Sn, or the like.

Here, a semiconductor layer doped with a dopant may be disposed betweenthe undoped semiconductor layer 130 and the first conductive typesemiconductor layer 140, but not limited thereto.

The active layer 150 is formed on the first conductive typesemiconductor layer 140 and has a single quantum well structure or amultiple quantum well structure. For example, the active layer 150 maycomprise one cycle or more of a quantum well layer 151 and a quantumbarrier layer 152. The quantum well layer 151 may be formed of InGaN,GaN, or InAlGaN, and the well barrier layer 152 may be formed of AlGaN,GaN, or InAlGaN, but not limited thereto. A light emitting material ofthe active layer 150 may vary depending on a light emitting wavelengthsuch as a blue wavelength, a red wavelength, a green wavelength, or thelike.

For example, the quantum well layer 151 and the quantum barrier layer152 may be formed of InGaN and AlGaN, respectively, by selectivelysupplying NH₃, TMGa (or TEGa), trimethylindium (TMIn), and TMAl as asource gas using N₂ as a carrier gas at a predetermined growthtemperature, e.g., a temperature ranging from about 700° C. to about950° C. Here, the quantum barrier layer 152 has an N-type semiconductorproperty although it is not doped. The quantum barrier layer 152 may bedisposed as the uppermost layer of the active layer 150, but not limitedthereto.

A conductive type cladding layer (not shown) may be formed on/under theactive layer 150. The conductive type cladding layer may be formed as anAlGaN layer.

The thin insulating layer 160 is formed on the active layer 150, and thesecond conductive type semiconductor layer 170 is formed on the thininsulating layer 160. Here, the thin insulating layer 160 is formed onthe quantum barrier layer 152 of the active layer 150.

The thin insulating layer 160 is a thin layer with an insulatingproperty, and may serve as a high resistive layer and a low conductivelayer compared with the second conductive type semiconductor layer 170.

The thin insulating layer 160 may be doped with a very small amount of aP-type dopant such as Mg, Zn, Ca, Sr, or Ba, or a group II element. Thethin insulating layer 160 may be a GaN thin insulating layer. Forexample, the GaN thin insulating layer may be formed by supplying NH₃and TMGa (or TEGa) as a source gas and supplying a P-type dopant such asMg at a predetermined temperature, e.g., 900° C. or more. The GaN thininsulating layer comprises a p-type carrier concentration ranging fromabout 5×10¹⁷/cm³ to about 5×10¹⁸/cm³. Here, an undoped GaN layercomprises N-type carriers of about 5×10¹⁶/cm³ though it is notintentionally doped. Therefore, a very small amount of the P-type dopantis provided in order to remove the N-type property when the GaN thininsulating layer is grown. Accordingly, the GaN thin insulating layercan have a perfect insulating property.

A hole concentration of the thin insulating layer 160, (that is, abackground hole concentration) may be about 5×10¹⁸/cm³ or less. Thebackground hole concentration means a hole concentration of theuppermost quantum barrier layer of the active layer 150, and the holeconcentration of the thin insulating layer 160 may be the holeconcentration of the quantum barrier layer 152, that is, about5×10¹⁸/cm³ or less.

The thin insulating layer 160 may be formed to a thickness ranging fromabout 1 nm to about 9 nm. Since the thin insulating layer 160 hasproperties of an insulating layer and a high resistive layer, holes thatmove from the second conductive type semiconductor layer 170 to theactive layer 150 may move in vertical and horizontal directions in thethin insulating layer 160. That is, since the movement speed of theholes in a horizontal direction is higher than that in a verticaldirection in the thin insulating layer 160, the holes to move to theactive layer 160 can be blocked and diffused.

Also, although the thin insulating layer 160 is formed as the GaN thinlayer, it may be formed as an insulating layer using at least one ofcompound semiconductors such as GaN, InN, AlN, InGaN, AlGaN, InAlGaN, orAlInN.

The second conductive type semiconductor layer 170 may be disposed as anelectrode contact layer doped with a second conductive type dopant onthe thin insulating layer 160. The second conductive type semiconductorlayer 170 may be formed as a P-type semiconductor layer, and the P-typesemiconductor layer may selectively comprise GaN, InN, AlN, InGaN,AlGaN, InAlGaN, AlInN, or the like. The second conductive type dopant isa P-type dopant, and the P-type dopant comprises Mg, Zn, Ca, Sr, Ba, orthe like. The second conductive type semiconductor layer 170 may have adoping concentration of about 5×10¹⁷/cm³ or more and a thickness rangingfrom about 500 Å to about 1000 Å, but not limited thereto.

An N-type semiconductor layer may be disposed as a third conductive typesemiconductor layer (not shown) on the second conductive typesemiconductor layer 170. In the first embodiment, the first conductivetype semiconductor layer 140 is an N-type semiconductor layer and thesecond conductive type semiconductor layer 170 is a P-type semiconductorlayer, but a reverse structure thereof may be formed. A light emittingstructure according to the embodiments may comprise one of a P—Njunction, an N—P junction, an N—P—N junction, and a P—N—P junction.

A transparent electrode layer may be formed on the second conductivetype semiconductor layer 170, and a second electrode layer is formed onthe transparent electrode layer. Here, in the case of an N—P—N junctionstructure, the transparent electrode layer may be disposed on the thirdconductive type semiconductor layer that is the N-type semiconductorlayer.

In the semiconductor light emitting device 100, since the thininsulating layer 160 is disposed between the active layer 150 and thesecond conductive type semiconductor layer 170, a current scarcely flowsat a low voltage of about 2.5 V or less and an operating current usingtunneling flows at only about 3 V or more. Also, since the holes arediffused in the thin insulating layer 160 and are injected into theactive layer 150, the active layer 150 can improve opticalcharacteristics such as the internal quantum efficiency. In addition,light can be emitted uniformly in an entire region of the active layer150.

FIG. 2 is a side sectional view of a semiconductor light emitting deviceaccording to a second embodiment. Like reference numerals refer to likeelements in the first and second embodiments, and the same descriptionsthereof will be omitted.

Referring to FIG. 2, a semiconductor light emitting device 100Acomprises a substrate 110, a buffer layer 120, an undoped semiconductorlayer 130, a first conductive type semiconductor layer 140, an activelayer 150, a first thin insulating layer 160, and a second conductivetype semiconductor layer 170A comprising a second thin insulating layer173.

The first thin insulating layer 160 is formed between the active layer150 and the second conductive type semiconductor layer 170A. The firstembodiment may be referred to for the first thin insulating layer 160.

The second conductive type semiconductor layer 170A comprises a second Aconductive type semiconductor layer 171, the second thin insulatinglayer 173, and a second B conductive type semiconductor layer 175. Thesecond A conductive type semiconductor layer 171 and the second Bconductive type semiconductor layer 175 may be formed as a P-typesemiconductor layer doped with a P-type dopant. The second conductivetype semiconductor layer 170A may have a doping concentration of about5×10¹⁷/cm³ and a thickness ranging from about 500 Å to about 1000 Å, butnot limited thereto.

The second thin insulating layer 173 may be formed between the second Aconductive type semiconductor layer 171 and the second B conductive typesemiconductor layer 175. The second thin insulating layer 173 has aninsulating property. Also, the second thin insulating layer 173 mayserve as a high resistive layer and a low conductive layer, comparedwith the second A conductive type semiconductor layer 171 and the secondB conductive type semiconductor layer 175.

The second thin insulating layer 173 is doped with a very small amountof a P-type dopant or a group II element to have an insulating property.Here, the second thin insulating layer 173 may be doped with a P-typecarrier concentration ranging from about 5×10¹⁷/cm³ to about 5×10¹⁸/cm³to have a hole concentration of about 5×10¹⁸/cm³ or less. A thickness ofthe second thin insulating layer 173 may be greater than about 0 nm, andless than or equal to about 9 nm.

The second thin insulating layer 173 may comprise at least one ofcompound semiconductors such as GaN, InN, AlN, InGaN, AlGaN, InAlGaN, orAlInN.

The second thin insulating layer 173 diffuses holes injected through thesecond B conductive type semiconductor layer 175, and then the firstthin insulating layer 160 diffuses the holes injected through the secondA conductive type semiconductor layer 171. Therefore, the holes injectedinto the active layer 150 can be diffused uniformly, thereby improvingthe internal quantum efficiency.

Also, each thin insulating layer may be disposed between secondconductive type semiconductor layers. In addition, the thin insulatinglayer may be disposed between the second conductive type semiconductorlayer and a transparent electrode layer. The forming position and thenumber of the thin insulating layer may be modified in the scope ofspirits of the embodiments.

FIG. 3 is a side sectional view of a lateral semiconductor lightemitting device using FIG. 1.

Referring to FIG. 3, a lateral semiconductor light emitting device 100Bcomprises a first electrode layer 181 on the first conductive typesemiconductor layer 140 and a second electrode layer 183 on the secondconductive type semiconductor layer 170. When a forward current isapplied to the first electrode layer 181 and the second electrode layer183, holes injected through the second conductive type semiconductorlayer 170 are diffused in the thin insulating layer 160, and theninjected into the active layer 150. Therefore, the holes can be injecteduniformly in an entire region of the active layer 150, thereby improvingthe internal quantum efficiency.

FIG. 4 is a side sectional view of a vertical semiconductor lightemitting device using FIG. 1.

Referring to FIG. 4, a vertical semiconductor light emitting device 100Ccomprises a reflective electrode layer 185 on the second conductive typesemiconductor layer 170 and a conductive supporting substrate 187 on thereflective electrode layer 185. The reflective electrode layer 185 maybe formed of one selected from Al, Ag, Pd, Rh, and Pt, and theconductive supporting substrate 187 may be formed of copper or gold, butnot limited thereto.

Here, the substrate 110, the buffer layer 120, and the undopedsemiconductor layer 130 that are illustrated in FIG. 1 are removed usinga physical or/and chemical method. According to the physical method, thesubstrate 110 may be separated by applying a laser with a predeterminedwavelength to the substrate 110, and the buffer layer 120 may be removedusing wet or dry etching. According to the chemical method, thesubstrate 110 may be separated by injecting an etchant into the bufferlayer 120. The buffer layer 120 and the undoped semiconductor layer 130may be removed using chemical etching. A first electrode layer 181 maybe formed under the first conductive type semiconductor layer 140.

FIG. 5 is a reverse current versus voltage graph for a related art LEDand an LED according to the first embodiment, and FIG. 6 is a forwardcurrent versus voltage graph for a related art LED and an LED accordingto the first embodiment.

Referring to FIGS. 5 and 6, under the same voltage condition, a forwardcurrent and a reverse current of the LED of FIG. 1 are lower than thoseof the related art LED. Therefore, the LED of FIG. 1 can decrease theleakage current.

Also, referring to FIG. 6, a current scarcely flows at a low voltage,e.g., about 2 V or less, and flows at about 3 V, which is an operatingvoltage of the LED, or more. That is, a current flows by tunneling atabout 3 V or more in the LED of FIG. 1.

FIG. 7 is a graph showing a reliability test for a related art LED andan LED according to the first embodiment for a predetermined time.

Referring to FIG. 7, a current constantly flows for a long time in theLED according to the first embodiment, thereby improving thereliability, compared with the related art LED.

In descriptions of the embodiments, it will be understood that when alayer (or film), a region, a pattern, or components is referred to asbeing ‘on’ or ‘under’ another substrate, layer (or film), region, orpatterns, it can be directly on the other layer or substrate, orintervening layers may also be present. Also, in the descriptions of theembodiments, sizes of elements illustrated in drawings are one example,and the present disclosure is not limited to the illustrated drawings.

Although embodiments have been described with reference to a number ofillustrative embodiments thereof, it should be understood that numerousother modifications and embodiments can be devised by those skilled inthe art that will fall within the spirit and scope of the principles ofthis disclosure. More particularly, various variations and modificationsare possible in the component parts and/or arrangements of the subjectcombination arrangement within the scope of the disclosure, the drawingsand the appended claims. In addition to variations and modifications inthe component parts and/or arrangements, alternative uses will also beapparent to those skilled in the art.

What is claimed is:
 1. A semiconductor light emitting device,comprising: a substrate; a first semiconductor layer including an n-typedopant on the substrate; an active layer having a multiple quantum wellstructure on the first semiconductor layer; a nitride-basedsemiconductor layer disposed between the active layer and the firstsemiconductor layer; a second semiconductor layer disposed on a topsurface of the active layer; a third semiconductor layer on a topsurface of the second semiconductor layer; a fourth semiconductor layeron a top surface of the third semiconductor layer; a first electrode onthe first semiconductor layer; and a second electrode on the fourthsemiconductor layer, wherein the second to fourth semiconductor layersinclude a p-type dopant, wherein the second and fourth semiconductorlayers are formed of a p-type semiconductor layer, wherein the p-typesemiconductor layer of the second semiconductor layer is formed of anInAlGaN semiconductor, wherein the third semiconductor layer is disposedbetween the top surface of the second semiconductor layer and a lowersurface of the fourth semiconductor layer, wherein the thirdsemiconductor layer has a concentration of the p-type dopant less thanthat of each of the second and fourth semiconductor layers, wherein thethird semiconductor layer is formed of a lower conductive layer thanthat of each of the second and fourth semiconductor layers, and whereinthe third semiconductor layer is formed of a GaN semiconductor.
 2. Thesemiconductor light emitting device of claim 1, wherein the thirdsemiconductor layer is physically contacted with the top surface of thesecond semiconductor layer and the lower surface of the fourthsemiconductor layer.
 3. The semiconductor light emitting device of claim1, wherein the third semiconductor layer has a thickness less than 9 nm.4. The semiconductor light emitting device of claim 1, wherein the firstsemiconductor layer is formed of a GaN semiconductor.
 5. Thesemiconductor light emitting device of claim 1, wherein the active layerincludes a barrier layers and a well layer, and wherein the barrierlayer has a hole concentration of 5×10¹⁸/cm³ or less.
 6. Thesemiconductor light emitting device of claim 1, wherein the thirdsemiconductor layer has the concentration of the p-type dopant of5×10¹⁷/cm³ or more.
 7. The semiconductor light emitting device of claim6, wherein the third semiconductor layer has a hole concentration of5×10¹⁸/cm³ or less.
 8. The semiconductor light emitting device of claim6, wherein a sum of thicknesses of the second to third semiconductorlayers is a range of 500 Å˜1000 Å.
 9. A semiconductor light emittingdevice, comprising: a substrate; an n-type semiconductor layer on thesubstrate; an active layer disposed on the n-type semiconductor layer; aplurality of p-type semiconductor layers on a first barrier layer of theactive layer; a first electrode connected to the plurality of n-typesemiconductor layers; a second electrode on the plurality of p-typesemiconductor layers; and a transparent electrode layer disposed betweenthe plurality of semiconductor layers and the second electrode, whereinthe plurality of p-type semiconductor layers includes a first layer onthe active layer, a second layer on the first layer and a third layer onthe second layer, wherein the second layer is disposed between the firstlayer and the second layer, wherein the first layer is formed of anInAlGaN semiconductor, wherein the second layer has a concentration of ap-type dopant less than that of each of the first and third layers,wherein the second layer is formed of a lower conductive layer than thatof each of the first and third layers, and wherein the second layer isformed of a GaN semiconductor.
 10. The semiconductor light emittingdevice of claim 9, wherein the second layer has a hole concentration ofabout 5×10¹⁸/cm³ or less and has a greater resistivity than that of thefirst semiconductor layer.
 11. The semiconductor light emitting deviceof claim 9, wherein the second layer is physically contacted with a topsurface of the first layer and a lower surface of the second layer. 12.The semiconductor light emitting device of claim 9, wherein the secondlayer has a thickness less than 9 nm.
 13. The semiconductor lightemitting device of claim 9, wherein the n-type semiconductor layer andthe third layer are formed of a GaN semiconductor.
 14. The semiconductorlight emitting device of claim 9, wherein the active layer includes aplurality of barrier layers and a plurality of well layers, and whereinthe first barrier layer adjacent to the plurality of p-typesemiconductor layers has a hole concentration of 5×10¹⁸/cm³ or less. 15.The semiconductor light emitting device of claim 9, wherein the secondlayer has a hole concentration of about 5×10¹⁸/cm3 or less and has athickness of greater than 0 nm and less than 9 nm.
 16. The semiconductorlight emitting device of claim 9, wherein the second layer has a greaterresistivity than that of each of the first and the third layers.
 17. Thesemiconductor light emitting device of claim 16, wherein the third layeris directly contacted with the transparent electrode layer.
 18. Thesemiconductor light emitting device of claim 9, wherein the second layerhas the concentration of a p-type dopant of 5×10¹⁷/cm³ or more.
 19. Thesemiconductor light emitting device of claim 18, wherein the secondlayer has a hole concentration of 5×10¹⁸/cm³ or less.
 20. Thesemiconductor light emitting device of claim 18, wherein a sum ofthicknesses of the first to third layers is a range of 500 Å˜1000 Å.